There have been proposed in recent years as a method for checking whether air pressure (internal pressure) of an air-inflated pneumatic tire for a passenger car is normal or not various types of tire pressure monitoring system (TPMS) each having an air pressure sensor provided in the interior of the tire for measuring tire internal pressure or the like of the tire so that the system is capable of receiving information on air pressure transmitted via wireless communication from the air pressure sensor by a reception device provided on a vehicle body side and expressing a warning when the air pressure has dropped beyond an acceptable range (e.g. PTL 1).